Liquid and gas mixtures have to be phase separated in order to remove liquid droplets from industrial gas streams to satisfy environmental standards (e.g., radioactive water from steam at nuclear power plants) or to purify gas streams, increase liquid recovery, and to protect rotating equipment located downstream (e.g., oil processing facilities, engine air intakes, gas processing plants). A complete phase separation will eventually occur without employing any mechanical devices given the effects of gravity and long contact times; however, to accelerate this process several separation techniques have been proposed. These techniques operate based on one or more physical forces accelerating fluid separation, such as inertial, gravitational, diffussional, centrifugal and electrostatic. Mechanical equipment operating on these principles include impingement separators (baffle, wire mesh, vanes), cyclones, knock-out pots, and filters, as described in U.S. Pat. No. 6,017,377, and wet precipitators, as described in U.S. Pat. No. 5,843,210.
The above separation techniques are selected based on the liquid collection efficiency requirement, gas flow rate and liquid loading, solid deposition tolerance, pressure drop, and capital cost. There is a need to develop liquid/gas separators that will achieve high level of liquid removal efficiency and throughput and at the same time minimize the amount of energy that is required to treat the gas (pressure drop) and minimize capital cost.
One of the most widely used gas/liquid separators are impingement separators. The basic elements of impingement separators are strategically located devices (targets) on which liquid droplets collide. The simplest impingement separators consist of a baffle or disk inserted against the vessel inlet. These separators provide low droplet removal efficiency but can remove bulk of the liquid entering the vessel. To improve efficiency and recovery of smaller droplets more sophisticated impingement separators have been developed. One type of these devices is vane-type separator that consists of parallel plates (see, e.g., U.S. Pat. Nos. 4,581,051 and 4,557,740) that are straight or bent creating flow channels. Typically, the channels are of uniform cross section across their entire length (see, e.g., U.S. Pat. No. 5,972,062). In these devices, liquid droplets present in the gas stream impinge on the plates due to inertia of the droplets and collect on the vane surfaces in the form of a film of liquid. This liquid film (recovered liquid) drains down the vane into the collection devices without re-entrainment. The channels also can be arranged radially using serpentine vanes (see, e.g., U.S. Pat. No. 5,112,375).
With reference now to FIG. 1, shown is a chevron-style impingement vane bundle or pack 10. As shown, chevron-style impingement vane bundles 10 include vanes 12 affixed to (e.g., welded) inside boxing 14. Two concavely-curved, horizontal plates or outlet baffles 16 are affixed to (e.g., welded) to the boxing 14, channeling the flow of gas so that the gas only flows through the vanes 12 from the inlet-side 18 of the vane bundle 10 towards the outlet-side 20 of the vane bundle 10 and to the outlet nozzle of the separator vessel (not shown). The boxing 14 and the outlet baffles 16 may be welded or otherwise affixed to the separator vessel walls to secure the vane bundle 10 to the separator vessel. The outlet baffles 16 are curved to fit the separator vessel walls and block the vertical flow of gas on the outlet-side 20 of the vane bundle 10. The area formed on the outlet-side of the vane bundle 10, between the vanes 12, outlet baffles 16 and the interior wall of the separator vessel may be referred to as the outlet chord area.
Chevron-style impingement vanes bundles 10 are widely used for the separation of liquid phase droplets from industrial gas streams. Often such vane bundles 10 are employed in vertical vessels in which the gas stream is directed to the vane bundle 10 from either below of from above the vane bundle 10. Several factors limit the amount of gas that can be fed to a given vane bundle 10 without encountering localized flooding in the vane pack 10 and liquid carryover from the separator.
One of these factors is the inlet chord area available between the vane boxing 14 edge on inlet-side 18 of the vane pack 10 and the interior wall of the vessel (not shown). If velocities in this chord area exceed certain values, the gas stream will not disperse itself evenly across the vane bundle 10 and flooding and carryover will occur. To increase the available chord area, vane packs 10 have been placed off center of the vessel centerline, towards the outlet nozzle of the separator vessel. This is done as the inlet chord area is more important to separator performance than is the outlet chord area.
There is a need to increase the inlet chord area even further to increase the amount of gas that can be fed to a given vane bundle without encountering localized flooding in the vane pack and liquid carryover from the separator.